Oscillatory circuit



@cfi. 15, 1935.

c. w. HANSELL 2,017,093

OSCILLATORY CIRCUIT Filed May 1, 1951 2 Sheets- Sheet 1 INVENTOR CLARENCE W. HANSELL ATTORNEY (kit. 15, 1935. Q w HANSELL 2,017,093

OSCILLATORY CIRCUIT Filed May 1, 1931 2 SheetsSheet 2 ill INVENTOR CLARENCE W. HANSELL ATTORNEY Patented Oct. 15, .1935

UNITED STATES 7 2,011,093 OSCILLATORYV cmcorr Clarence W. Hansell, Port Jefferson, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application May 1, 1931, SerialNo. 534,255

10 Claims.

This invention relates to apparatus for generating high frequency undulatory electrical currents and in particular relates to new and'useful circuits employing electron discharge devices .for generating high frequency oscillations and resonant long line means for frequency control.

In my United States Patent No. 1,945,546, granted February 6, 1934, I have described a sys tem employing resonantlong line frequency control whereby, by the use of a transmission line, long, relative to the working wave length coupled to an oscillation generator, the frequency of oscillations generated by the generator are maintained constant and depend, in the main, upon the length of the line employed. That is, by making the line a large number of half wave lengths long, the frequency controlling action of the line may be attributed to the fact that the line forms the equivalent of a sharply tuned resonant circuit whose reactance changes rapidly with change of frequency and which change of reactance may be utilized to keep the frequency of an oscillator relatively constant. Since the resonance frequency of the line and the circulating current in it is determined chiefly by the length of the line, and since the length is substantially constant, a high degree of frequency stability is obtained.

It is an object of my present invention to provide an oscillation generator having resonant long line control, the long line being grounded at both of its ends.

A further object of my present invention is to provide an electron discharge oscillation generator having resonant long line control applied to its input circuit and an inductively coupled tunable circuit for exciting the line.

Still a further object of my present invention is to provide an improved form of resonant line associated with an electron discharge device oscillator which line shall be radiationless and free from pick-up of extraneous alternating current energies which might affect the operation of the oscillator. According to the present invention the resonant line is made of an inner conductor and, preferably, a concentric hollow outer conductor whereby standing waves on the conductors, beingout of phase, neutralize each other thereby preventing radiation.

Still a further object of my present invention is to provide an electron discharge device oscillator, resonant long line frequency controlled, with means associated with the line for establishing bias on electrodes of the oscillator through connections made at points of substantially zero radio frequency potential.

Other objects as well as advantages of my present invention will become apparent as the description thereof, which will be given with the aid of the accompanying drawings, proceeds.

In the drawings, 5..

Figure 1 illustrates an oscillator having resonant long line control means, the line being grounded at both its ends,

Figure 2 illustrates a similar oscillation generator wherein feed to the line is accomplished through inductive coupling and a tunable circuit,

Figure 3 illustrates a similar frequency controlled oscillator wherein the line is made of radiationless, concentric conductors, and,

Figures 4, 5 and 6 illustrate oscillators of the 15 pushpull type wherein electrode bias is supplied by connection from the biasing means connected to points of substantially zero radio frequency potential.

Turning to Figure 1, an electron discharge de- 20 vice oscillator 2 has in its output circuit a tunable circuit 4. Oscillation generation is maintained by feed back through the interelectrode capacity of the device 2 as well as transfer of energy through the long resonant transmission grounded at both of its ends as shown, and coupled to theanode of device 2 through blocking condenser 8 and to the grid of device 2, through the condenser Ill. The grid is maintained at a suitable bias by the action of resistor 12.

As described more fully in my copending application referred to, standing waves on the long transmission line 6 whose conductors are preferably shielded so as to prevent radiation and energy pick-up, pull the oscillations generated by the oscillator 2 to a frequency corresponding to a resonance frequency of the line for, the conditions under which it is operated. As the ends of the line are grounded, the tapping points to the anode and grid should be adjusted'at a dis- 40 tance away from the grounding points whereby optimum operating conditions are obtained. That is, by adjusting the tap at the input end of the line the amount of oscillating current in the line may be adjusted. Usually this adjustment 5 will be such that theuseful output from the oscillator together with the losses in the line will put normal load on the vacuum tube. The amount of grid excitation will be adjusted to the normal value by adjusting the tapon the output end of 50 the line. The exact adjustment of frequency, after all other adjustments are made, will be made by varying the length of the line or the tuning of the anode circuit.

By keying or modulating the input circuit of line 6 through a blocking condenser 20 as shown, to ,a

power amplifier system 22 which may contain frequency multipliers, and then radiated'by a suitable antenna 24. Of course, if desired, the

modulation may also be introduced'm the'amplifier system. 7

Turning to Figure 2, the resonant line may be inductively coupled to the anode .high frequency .choke coil 26 by means of the coil forming part. of the tunable circuit 28. 'The grid ofioscill'ator 2 is, of course, maintained ,at a potential other than that of ground potential by the action of blocking condenser 30 and by the use of choke and condenser resistance, combination 34 between the grid and cathode of tube 2. Output energy may be taken from the oscillator by inductive coupling or through a blocking condenser 36 and utilized in any desirable fashion. It will be understood that the condenser of circuit'28 may be connected in series with the coupling coil instead of in parallel as shown, or that the condenser may be omitted entirely and the length of line changed to compensate for its omission.

Referring to Figure 3, the long line 6 is made up of an inner conductor 38 and an outer concentric conductor or .pipe 40 both being joined together for radio frequency currents by blocking condenser 42. The long line, as shown isconnected across the grid to cathode resistor 44 whereby it exerts a controlling. effect upon the frequency of oscillations generated. It should be understood that resistor 44 may have a choke coil in series and a condenser. in parallel with it for biasing purposes. Also the condenser 42, or the length of connections to it maybe made variable for obtaining exact adjustment of frequency, or, if desired, the line may have a slidably adjustable section, like a trombone to serve the same purpose. By virtue of the concentric arrangement of the resonant line, radiation or pickup from other sources is prevented. The inherent capacity of electron discharge device 2 is indicated by the dotted lines, and, if this is insufli cient to start oscillations it may be supplemented by a capacity connected in parallel to the anode and grid of tube 2. As indicated, output energy may be taken from a circuit 46 inductively coupled to the tuned output circuit 4 of electron discharge device oscillator 2. Obviously, any of the other well known methods of coupling may also be used. I

Figure 4 illustrates a long line frequency controlled oscillator which has been used in actual practice. Electron discharge devices 48, 50 which may be either the air cooled or liquid cooled type have a resonant long line 6 coupled to the input electrodes thereof and a tunable output circuit 52 connected across the anodes. Through the action of resistor- 54 connected between the cathodes and the grids andconnectedto the varineutralizing condensers 58 the amount of feed back may be controlled at'w-i-ll. If desired, these neutralizing condensers may be omitted and the regeneration adjusted by varying the length of the line 6 and the tuning of circuit 52 by such relative amounts as to keep the frequency fixed.

Modulation may be accomplished by varying 5 the current flow through the modulating tubes 60 whereby the current flow through the oscillators 48, 50, is varied inasmuch as the current flow through the choke 62 must remain substantially constant. The output from a suitable cir- 10 cuit 52 may be directly radiated, or, may be further amplified and frequently multiplied by the use of additional amplifier 64 and thence radiated over a suitable antenna 66. Preferably, the

antenna should be directive. It

In order to check the frequency of oscillations of the system shown in Figure 4, the radio frequency amplifierfi8 may be coupled to any oscillating portion of the system so that its output feeds a detector 70 also supplied with energy of 20 known frequency from, say a crystal controlled harmonic generator 12. The frequency of the beat resulting from the two sources of energy may then be indicated in a suitable indicating device '14, and, by adjustment of slider 56, so that the 25 beatv becomes of a desired value, the transmitter may be adjusted to any suitable or desirable operating frequency. Obviously, the frequency checking and monitoring device may also be used with any of the other oscillators described. 30

Of course, various minor changes may be made to the arrangement shown in Figure 4. Thus, a parallel tuned input circuit may be connected across the grids and the resistor 54 connected from a mid-point of the tunable input circuit to the cathodes for maintaining correct bias. Moreover, this mid-point connection may be grounded by the use of a condenser for radio frequency potentials. The long resonant line may then be inductively or conductively coupled to the tunable input circuit.

Moreover, the long line shown in Figure 4 may be made of concentric conductors as shown in Figure 3., variable adjustment being accomplished by the use of a disk or other suitable device within the outer conductor contacting with both the outer and the inner conductor and being slidable within and alongthe outer conductor.

' In the arrangement shown in Figure 5, a long resonant, transmission line 6 couples the output one-half wave length long, the wave length taken being that of a desired operating frequency. The anode potential may be supplied through radio frequency choke 82 and lead 84 upon which signal voltages are impressed through the action of a. transformer 86. Output energy may, of course, be taken through blocking condensers 88 to transmission line 90 and utilized as desired.

Figure 6 illustrates an oscillator which has been 5 found useful for producing very high radio frequencies. A long resonant line 6 is coupled to the grid electrodes of electron discharge devices 48, 59 and another long resonant line 1 preferably of a length different from 6, is coupled to the output are supplied through a lead 84 and fed to. the anr odes through the long resonant line 1-, Output energy may be taken from the resonant line through transmission linev 9G and radiated from a suitable antenna or radiator 92.

In order to start and maintain oscillations at the frequency higher than the lowest frequency for which the circuits are resonant, a circuit such as circuit 9 is coupled to the oscillators d8, '59. This circuit has a low power factor and a minimum resonant frequency equivalent to the free quency desired. For a suitably designed circuit and proper coupling to the oscillators, the system will operate at the frequency desired. Customarily the circuit 94 takes the form of a U-shaped piece of copper a half wave length long at the desired oscillation frequency and is coupled capacitively as shown to the oscillators 48, 58. This circuit is described. more fully in the copending application of Nils E. Lindenblad, Serial Number 486,375, filed October 4, 1930.

Having thus described my invention, what I claim is:

1. An electron discharge device oscillator comprising an electron discharge device having an anode, a cathode, and a control electrode, a transmission line having uniformly distributed inductance and capacity and being a plurality of half wavelengths long at the wave length of a desired operating frequency, an output impedance connected between'said anode and cathode, and, a tunable circuit connected to said line, the circuit and line being connected between said control electrode and cathode, said tunable circuit being coupled to said output impedance for supplying energy to said line whereby standing waves on said line react to pull the oscillations generated by said device to a frequency where the line, as modified by its associated circuits, is substantially resonant.

2. An electron discharge device oscillator comprising an electron discharge device having an anode, a cathode, and a control electrode, a long resonant transmission line connected between said control electrode and cathode, said line being substantially a whole number of half wavelengths long at a desired operating frequency, a resonant tunable circuit connected in series with said long resonant line, and, an inductance coil connected to said anode coupled to said tuned circuit for establishing feed back from said anode to said control electrode.

3. An electron discharge device oscillator com prising an electron discharge device having an anode, a cathode, and a control electrode, a long resonant transmission line connected between said control electrode and cathode, said line being substantially a whole number of half wavelengths long at a desired operating frequency, a parallel resonant tunable circuit connected in series with said long resonant line, and, an inductance coil connected to said anode coupled to said parallel tuned circuit for establishing feed back from said anode to said control electrode.

i. An electron discharge device oscillator comprising an electron discharge device having an anode, a cathode, and a control electrode, a long resonant transmission line connected between said control electrode and cathode, a resonant tunable circuit, consisting of an inductor and a capacitor connected in series with said resonant line, said line being a plurality of half wavelengths long at a'desired operating frequency, and, an inductance coil connected to said anode coupled to the inductor of said tuned circuit for establishing feed back from said anode to said control electrode. 0

5; An electron discharge device oscillator comprising an electron-discharge. device having an anode, a cathode,.an'd' a control electrode, a long resonant transmission line having uniformly distributed inductance and capacity connected between said control electrode and cathode, said line being substantially linear and being a plurality of half wavelengths long at a desired operating frequency, an inductance coil connected in series with said long resonant line, and, 'an inductance coil connected to said anode coupled to said first mentioned inductance coil for establishing feed back from said anode to said control electrode.

6. An electron discharge device oscillator comprising an electron discharge device having an anode, a cathode and a control electrode, said anode and control electrode being regeneratively coupled together, a resistance connected across said cathode and control electrode, an inductor connected between said anode and cathode, and a resonant transmission line consisting of a pair of substantially straight parallel conductors having uniformly distributed inductance and capacity connected to said resistance, said line being substantially a whole number of half wavelengths long at a desired operating frequency and acting to stabilize the frequency of oscillations generated by said electron discharge device.

'7. An electron discharge device oscillator comprising an electron discharge device having an anode, a cathode and a control electrode, said anode and control electrode being regeneratively coupled together, a resistance and a radio frequency choke coil connected in series, said series connection being connected across said cathode and control electrode, a resonant transmission line consisting substantialy of two substantially straight parallel conductors having uniformly distributed capacity and inductance substantially a whole number of half wavelengths long at a desired operating frequency connected to said resistance and radio frequency coil, said line acting to stabilize the frequency of oscillations generated by said device.

8. An electron discharge device oscillator comprising an electron discharge device having an anode, a cathode and a control electrode, said anode and control electrode being regeneratively coupled together, a resistance and a radio frequency choke coil connected in series, said series connection being connected across said cathode and control electrode, a condenser connected across said resistance, a circuit having inductance and capacity connected between said anode and cathode, a linear transmission line consisting of substantially two conductors substantially parallel and substantially straight and having substantially uniformly distributed inductance and capacity, substantially a whole number of half wavelengths long at a desired operating frequency connectedto said resistance and radio frequency coil, said line acting to stabilize the frequency of oscillations generated by said electron discharge device.

9. An electron discharge device oscillator comprising an electron discharge device having an anode, a cathode, and a control electrode, means establishing coupling between said control electrode and anode, a resistance and a radio frequency choke coil connected in series across said cathode and control electrode, a condenser connected across said resistance, and a long resonant 7 transmission line substantially a. whole number of half wavelengths long at a desired operating frequency connected across said resistance and. radio frequency coil for stabilizing the frequency of oscillations generated by said electron discharge device. l

10. An electron discharge device oscillator comprising an electron discharge device having an anode, a cathode and a grid, a resistance con-- nected between said grid and cathode, and, a resonant transmission line consisting substan- I CLARENCE W. HANSELL. 

